1. Field of the Invention
The present invention proposed in this specification relates to a method for reproducing the quantization precision of a digital signal. The present invention is achieved, so as to be used, as one of the functions of a quantization-precision-reproduction device, an image-pickup device, and an information-processing device. Further, the present invention is achieved, as a program adapted to control the above-described devices.
Here, the digital signal for processing includes a signal in an ultimate form acting on the sensory organs of a person, such as a video signal, an audio signal, and so forth, a signal transmitted from a measuring device, a communication signal, and data read from a recording medium.
2. Description of the Related Art
When an analog signal is converted into a digital signal, the information amount of the digital signal is determined by a sampling frequency and the quantization-bit number. The sampling frequency determines the maximum frequency that can be represented by Nyquist's theorem and the quantization-bit number determines precision in an amplitude direction. Namely, the quantization-bit number determines the minimum change amount of the digital signal.
If the determined minimum change amount is too large with reference to a signal for representation, a quantization distortion is perceived by a person. Therefore, it is favorable to increase the number of quantization bits for an output signal, so as to reproduce an image with smooth gray scale.
In general, however, the performance of an analog-to-digital conversion (A/D conversion) device is limited. Therefore, it is difficult to increase the quantization-bit number appropriately. Further, it is often difficult to use an A/D converter configured to achieve a large number of quantization bits from the viewpoint of the manufacturing cost.
Subsequently, there have been proposed methods for reducing the quantization distortion, which is useful in the case where the quantization-bit number is insufficient with reference to the dynamic range of an input signal.
For example, there has been proposed a method for increasing the bit number in the least-significant-bit direction and inserting a random noise into the part corresponding to the increased bit number.
Further, there has been proposed a method for switching between an output signal transmitted from a low-pass filter and an original signal according to the characteristic of the original signal.
For example, Japanese Unexamined Patent Application Publication No. 2003-259368 discloses technologies relating to the above-described methods.